Once more into the snapshot diff cauldron

[epugh]

Description

Asked Claude to simplify and refactor our diff code to treat a snapshot as just another "searcher" . Boom and it worked!!!

Motivation and Context

We want to store every try as a snapshot, and have code that supports that in https://github.com/o19s/quepid/pull/1313. We tried an attempt at this in https://github.com/o19s/quepid/pull/1323 and it was a terrible stew of broken hopes and dreams.

How Has This Been Tested?

Manual mostly, and added a test.

Screenshots or GIFs (if appropriate):

Types of changes

• [] Bug fix (non-breaking change which fixes an issue)
• [x] Improvement (non-breaking change which improves existing functionality)
• [] New feature (non-breaking change which adds new functionality)
• [] Breaking change (fix or feature that would cause existing functionality to change)

[Copilot]

@epugh I've opened a new pull request, #1572, to work on those changes. Once the pull request is ready, I'll request review from you.

[epugh]

The original ticket: https://github.com/o19s/quepid/issues/833